Close taling microphone



y 1951 A. H. KLER CLOSE TALKING MICROPHONE Filed Feb. 27, 1948 INVENTOR ALFED H.KETTLER ATTOI QNEY Patented July 10, i951 UNITED STATES PATENT OFFICE 2,560,354 CLOSE TALKING MICROPHONE Alfred H. Kettler, Collingswood, N a .L, assignor to Radio Corporation of America, a corporation of Delaware Application February 27, 1948, Serial No. 11,511

6 Claims.

phone usage, while yet maintaining a desired fre-' quency response performance. Such a microphone may operate in response to either the pres sure of a sound wave or inresponse to-the first or second derivative of the sound Wave pressure. The pressure type depends solely on theextreme- 1y small talking-distance to obtain an increased speech signal, the efiective distance from the lips to the diaphragm often being less than inch. In addition to the distance effect, the gradien types of microphones are sensitive to the rate of pressure change with distance, which becomes Very high close to a sound source, and are also directional in their response. Hence, the sensitivity of the gradien microphones to speech compared with noise is very high, resulting in the popular terms, anti-noise, or noisecancelling being applied to them.

It is recognized that many of the important word endings, as Well as speech sounds, involve strong nasal resonances and radiation of sound from the nose. As constructed heretofore, close talking microphones have been responsive pri= marily to sound energy emanating from a persons mouth without regard to sound energy emanating from a persons nose in the normal:

too far from and in the null plane of the vibratile element. I

It is therefore, a primary object of my inven tion to provide a close talking microphone which will overcome the objectionable lack of) nasal quality, by picking up speech sounds emanatingfrom a personsnose in addition to those emanat ing. from the persons mouth, without impairing the anti-noise qualities oflthemicrophone.

It is another object of my invention to provide a close talking microphone wherein sound energy from the nose will not lie in the null plane of the vibratory element nor originate too far from.

the vibratile element. 7 l

A further object of my invention is to provide, in a microphone having a casing in which the vibratile element is enclosed, a method of obtaining more natural speech-pickup by suitably orienting the pickup or vibratile element and arranging apertures in the casing so that sound energy may be picked up from the users nose as well as the users mouth.

Another object of my invention is to improved type of close talking microphone which;

,- will be eificient, effective, easy to construct, and

one that will provide improved speech pickup.

In accordance with my present invention, I provide an improved close talking microphone comprising a housing and an electro-acoustical transd'ucer mountedin the housing. I also provide anarrangement of openings in the housing such that they may be located adjacent to independent sound sources originating from the mouth and nose of a user in order that sound energy may be independently transmitted from each of these sources by the most direct and shortest path to the transducer. In accordance with one form or my present invention, I employ a first order gra'idieht transducer comprising a vibratile element mounted in an apertured casing and operatively connected to an electro mechanical converter by a drive rod. The electro-mechanical converter may be of any suitable type which will transform sound energy into electrical energ upon vibration of the vibratile and drive rod elements. I

arrange the transducer in the microphone lionswith another embodiment ofresent inye ii tiofi, I em loy a second order gradient transducer in the same manner as the aforementioned first-order gradient transducer. The second order gradient microphone is composed or: two unitseach one being similar in construction to-the first order gradient transducer;-

The secondordergradient microphone includes two vibratile eIements each of which mounted in an apertureci casing and. operatively connected by a separate drive rod to an electromechanical converter. In this second embodiment, I also provide an arprovide an e rangement of the transducer units in the microphone housing and an arrangement of apertures in the casing enclosing the vibratile elements such that sound energ will be received by opposite sides of each of the vibratile elements at different time intervals thereby to create the necessary difference in phase to vibrate each of the vibratile and drive rod elements.

The novel features that I consider characteristic of my invention are set forth with greater particularity in the appended claims. The invention itself, however, both as to its organization and method of operation, as well as additional objects and advantages thereof, will best be understood from the following detailed description of several embodiments thereof, when read in connection with the accompanying drawing, in which Fig. 1 is a side elevation view of a close talking microphone constructed in accordance with my present invention and illustrating its position during use with respect to a users nose and mouth,

Fig. 2 is an enlarged top plan view of the microphone shown in Fig. 1,

Fig. 3 is an enlarged side elevation, partly in section, showing a microphone of the type illustrated in Fig. 2 and utilizing a first order gradient microphone in accordance with one embodiment of my present invention, and

Fig. 4 is a view similar to Fig. 3 but illustrating another embodiment of my present invention in which a gradient microphone of the second order is employed.

Referring more particularly to the drawing, I have illustrated two embodiments of my invention using similar reference numerals to designate corresponding parts for each embodiment.

In accordance with one form of my invention, I have shown, in Fig. 3, a close talking microphone I comprising an electro-acoustical signal translating apparatus in the form of a pressure gradient type transducer 3, and a protective mounting or outer casing 5 surrounding the transducer. The transducer 3 is composed of a vibratile element I connected to a drive rod 9, the latter being operatively connected to an electro-mechanical converter II of any suitable type for generating signal currents in well known manner upon vibration of the vibratile element 1 and its rod 9. The vibratile element 1 is enclosed in an inner protective casing I3 and arranged to divide the casing into separate chambers. The casing I3 is provided with one or more apertures I5 in its back wall and one or more apertures H in its front wall to communicate with th separate chambers and permit sound waves to reach the vibratory element.

In the pressure gradient type of microphone, it is essential to proper operation that the vibratile element be arranged so that both sides of the element are open to the source of sound. When arranged in this manner, the difference in sound pressure, due to a difference in phase between the pressures on the two sides of the vibratile element, is the source of the force which drives the element. Therefore, in order that a difference in phase may be created in the case of sound energy originating from two independent sound sources travelling in transverse paths, as for example sound energy from the mouth and nose sources, the openings in the housing enclosing the vibratile element must be arranged so' that the pressure from the sound waves will reach opposite sides of the element at different time intervals.

In practice, the finite size of the transducer also introduces a difierence in the magnitude of the sound pressure on the two sides when the effective talking distance is small compared to the transducer dimensions. The resultant drivin force will be greater, in general, than the force resulting from the phase effects. Therefore, in

order to obtain the correct effective distance from the source of the sound energy originating frcm'a persons nose to the vibratile element, it is necessary to provide a separate and more direct path for the sound waves from the nose to the vibratile element.

To this end, I have provided the transducer supporting structure or mounting 5 with a front opening I8 over which is placed a screen I9 and a back opening 20 over which is placed a screen 2| whereby the sound energy from a persons nose and mouth may be directed over the shortest and most direct paths to the vibratile element. In the form of my invention shown in Fig. 3, I have arranged the openings so that the opening I8 with its screen I9 will normally be positioned adjacent to and directly in front of the users mouth, and the opening 20 with its screen ZI will normally be positioned adjacent to and directly beneath the users nose, as illustrated in Fig. 1. This arrangement will then permit sound energy to be transmitted directly;

to the transducer 3 from both the mouth and the nose.

In order that the sound energy from each of the sources may be transmitted to both sides of the vibratile element 1 at different time intervals and thereby create a difference of pressure between the two sides of the vibratile element, I have arranged the transducer 3 so that its axis will be angularly related to each of the sound paths when the microphone I is being used. I have also arranged the apertures I5, I! in the casing I3 surrounding the vibratile element in a manner whereby the one group of apertures I5 will be located near the top of the transducer 3 on the side of the casing I3 away from the users mouth, and the other group of apertures I! will be located near the bottom of the transducer 3 on the side of the casing adjacent the users mouth, or, in other words, the apertures I5 will be out of registry or offset with respect to the apertures I'I. These arrangements will provide the necessary differences in path distance from each source of the sound energy to each side of the vibratile element. This construction will also permit the sound energy from each source to be transmitted to the vibratile element by a direct path, and will prevent the sound energyfrom lyin in the null plane of the vibratile element.

Inasmuch as it is desirable that the vibratile element I be operated at a fixed distance from the source of the sound energy, I have provided a bar 23 on the mounting 5 of the microphone I which will be of assistance in maintaining this distance. The bar 23 is preferably located near the top of the microphone I on the side of the mounting 5 adjacent the mouth of the user.- The bar 23'is composed of a central bowed portion 25 which extends across and adjacent to the top of the mounting 5, and two end portions 21,

29 integrally attached and extending at substantially right angles to each end of the bowed portion. Each of the end portions 21, 29 is mounted on the mounting .5 by any suitable mounting means. The bar 23 is also arranged at an angle to the front of the mounting, whereby it may be positioned to comfortably rest against the upper lip of the user in the region adjacent the users nose. The bar 23 may be positioned so that it will neither interfere with the normal movement of the lips for speaking, nor interfere with the sound energy from either source, and at the same time it will assist the user to maintain the microphone in its proper operating position.

In accordance with-a second embodiment of my invention, illustrated in Fig. 4 of the drawing, I use a pressure gradient transducer of the.

second order 3| which is provided with a mounting or casing 33 similar to the mounting or casing 5 in the embodiment of my invention illustrated in Fig. 3 of the drawing. The mounting 33 is provided with openings 34 and 36 which are similar to the openings |8 and 20, and which are covered, respectively, by screens 35 and 3 1, the openings 34 and 36 performing the same function as the openings l8 and 2|).

The second order gradient transducer 3| may be mounted in the casing 33 by any suitable mounting means, and comprises two units 39, 4|, each of which is similar to and functions the same as the transducer 3 shown in Fig. 3. The units 39, 4| are composed of vibratile elements 43, 45, respectively mounted in inner protective casings 41, 49. The vibratile elements 43, 45 are respectively connected to drive rods 5!, 53 which, in turn, are operatively connected to an electromechanical converter 55 of suitable type for generating signal currents upon vibration of the elements 43, 45 and their rods 5|, 53. The casings 41, 49 are constructed similar to the casing l3, having apertures whereby sound waves may reach opposite sides of the vibratile element to thereby actuate it. Thus, the casing 41 is provided with apertures 51 in the front side which faces a users mouth, and apertures 59 in the opposite or rear side. Similarly, the casing 49 is provided with apertures 6| in the front side facing a users mouthand apertures 63 in the opposite or rear side.

As in the case of the close talking microphone shown in Fig. 3, the mounting 33 for the second order gradient transducer 3| has the opening 34 located so that in use it will normally lie adjacent to and in front of the users mouth. while the opening 36 is located so that it will normally be positioned adjacent to and beneath the users nose, thereby providing the shortest path for transmission of sound energy to the vibratile elements 43, 45 from each of the sound sources.

In order that the sound energ from each of the sound sources will be received on opposite sides of the vibratile elements 43, 45 at different time intervals to create a difference of pressure on the two sides of each of the vibratile elements, I have arranged the units 39, 4| offset with respect to each other, and at a slight angle to a vertical plane passing through the transducer 3| parallel to the front and back thereof. I have also so arranged the apertures 51, 6| that they will be located near the bottom of the casings 41, 49, on the sides adjacent to a users mouth, and the apertures 59, 63 so that they will be located near the top of the casings 41, 49, on the sides away from a users mouth. This arrangment provides the necessary differences in distance from each source of the sound energy to each side of the vibratile elements whereby a difference in pressure on both sides of the vibratile elements may be created.

There is also provided on the mounting 33 a bar 65 which serves the same purpose as and which is similar in construction to the bar 23.

In accordance with my invention, it will be understood that I have constructed a close talking microphone of the pressure gradient type which provides an improved method of obtaining more natural speech pickup. The construction of my improved microphone permits sound energy to be picked up directly from the nasal source with equal efliciency and effectiveness as that from the mouth source. While I have illustrated two embodiments of my invention, I do not wish to be limited in this respect. It will be apparent to those skilled in the art that it is also possible to apply my invention to other forms of close talking microphones, as well as providing other arrangements of parts having equiv-- alent results. Therefore, I desire that the above description together with the drawing be con-- sidered as illustrative and not as limiting.

What is claimed is: 1

1. A microphone suitable for picking up sound from two closely disposed sound sources which project sound waves along paths transverse to each other, said microphone comprising an outer casing having openings for receiving and transmitting said sound waves from each of said sources, electro-acoustical transducer means carried by said casing for receiving and translating said sound waves into electrical energy, said transducer means comprising (1) an electromechanical converter, (2) an inner casing within said outer casing, (3) vibratile means mounted in said inner casing and dividing said inner casing into separate chambers, and (4) means operatively connecting said vibratile means to said converter, opposite sides of said inner casing having openings therein communicating with individual ones of said chambers, the openings communicating with one of said chambers being out of registry with the openings communicating with the other of said chambers so as to provide a difference in path distance for said sound waves from each of said sources to opposite sides of said vibratile means.

2. A microphone according to claim 1, characterized in that certain ones of said openings are located in the front wall adjacent the bottom of said inner casing for positioning in close proximity to and in front of the mouth of a user of said microphone, other ones of said openings are located adjacent the top and on the back of said inner casing for positioning in close proximity to and beneath said users nose.

3. In signal translating apparatus of the close talking type for picking up sound waves from a persons nose and mouth, the combination of casing means having openings therein, and electro-acoustical transducer means carried by said casing for translating sound wave energy into electrical energy, separate ones of said openings in said casing communicating with opposite sides of said transducer means, said transducer means comprising (1) an electro-magnetic converter mounted in said casing means, (2) an inner casing within said first named casing means having apertures therein, (3) at least one vibratile element mounted in said inner casing and being operatively connected to said converter, and said apertures in said inner casing being located in opposite sides of said inner casing and being out of registry one with the other so as to provide a difference in path'distance for said sound waves from said persons nose and mouth to each side of said vibratile element.

4.' In signal translating apparatus of the close talking type, the combination of a transducer supporting structure, and at least two transducer units mounted in said supporting structure, each of said units comprising a casing having apertures in opposite sides thereof and a vibratile element mounted in said casing, said vibratile elements being disposed in different planes, said supporting structure having openings therein for transmitting sound Waves along separate paths to each of said units, one of said openings being located in said structure so as to transmit sound waves from the mouth of a user of said apparatus to each of said units primarily along certain of said paths, another of said openings being lo- .cated in said structure so as to transmit sound waves from the nose of said user to each of said units primarily along certain other ones of said paths, and said casing apertures being arranged so as to provide sound Wave paths having difierent transmission time intervals to opposite sides of said vibratile elements from each of said sound sources.

5. Signal translating apparatus according to claim 4 characterized in that the axis of each of said vibratile elements is angularly related to each of said sound Wave paths.

6. A microphone of the pressure gradient re- 8 sponsive type comprising a casing having front and back walls spaced from each other, and a vibratory, sound responsive element mounted within said casing in spaced relation t each of said walls, said walls each having at least one opening therein providing communication from the exterior of said casing to said vibratory element, the opening on one side of said vibratory element being offset with respect to the opening on the opposite side of said vibratory element.

ALFRED H. KETTLER.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 730,101 Dunihue June 2, 1903 1,474,100 Aagaard Nov. 13, 1923 1,546,749 Roberts July 21, 1925 1,563,586 Pierman et a1. Dec. 1, 1925 2,271,988 Olson Feb. 3, 1942 2,346,395 Rettinger Apr. 11, 1944 2,390,488 Alford Dec. 11, 1945 2,406,119 Williams et al. Aug. 20, 1946 2,485,405 OIney et al Oct. 18, 1949 FOREIGN PATENTS Number Country Date 506,668 Great Britain June 1, 1939 

